Immunochip identifies novel, and replicates known, genetic risk loci for rheumatoid arthritis in black South Africans

Mol Med. 2014 Aug 14;20(1):341-9. doi: 10.2119/molmed.2014.00097.

Abstract

The aim of this study was to identify genetic variants associated with rheumatoid arthritis (RA) risk in black South Africans. Black South African RA patients (n = 263) were compared with healthy controls (n = 374). Genotyping was performed using the Immunochip, and four-digit high-resolution human leukocyte antigen (HLA) typing was performed by DNA sequencing of exon 2. Standard quality control measures were implemented on the data. The strongest associations were in the intergenic region between the HLA-DRB1 and HLA-DQA1 loci. After conditioning on HLA-DRB1 alleles, the effect in the rest of the extended major histocompatibility (MHC) diminished. Non-HLA single nucleotide polymorphisms (SNPs) in the intergenic regions LOC389203|RBPJ, LOC100131131|IL1R1, KIAA1919|REV3L, LOC643749|TRAF3IP2, and SNPs in the intron and untranslated regions (UTR) of IRF1 and the intronic region of ICOS and KIAA1542 showed association with RA (p < 5 × 10(-5)). Of the SNPs previously associated with RA in Caucasians, one SNP, rs874040, locating to the intergenic region LOC389203|RBPJ was replicated in this study. None of the variants in the PTPN22 gene was significantly associated. The seropositive subgroups showed similar results to the overall cohort. The effects observed across the HLA region are most likely due to HLA-DRB1, and secondary effects in the extended MHC cannot be detected. Seven non-HLA loci are associated with RA in black South Africans. Similar to Caucasians, the intergenic region between LOC38920 and RBPJ is associated with RA in this population. The strong association of the R620W variant of the PTPN22 gene with RA in Caucasians was not replicated since this variant was monomorphic in our study, but other SNP variants of the PTPN22 gene were also not associated with RA in black South Africans, suggesting that this locus does not play a major role in RA in this population.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Arthritis, Rheumatoid / genetics*
  • Black People / genetics*
  • DNA-Binding Proteins / genetics
  • DNA-Directed DNA Polymerase / genetics
  • Female
  • Genetic Predisposition to Disease*
  • Genotype
  • Humans
  • Immunoglobulin J Recombination Signal Sequence-Binding Protein / genetics
  • Inducible T-Cell Co-Stimulator Protein / genetics
  • Interferon Regulatory Factor-1 / genetics
  • Male
  • Polymorphism, Single Nucleotide
  • Protein Tyrosine Phosphatase, Non-Receptor Type 22 / genetics
  • Receptors, Interleukin-1 Type I / genetics
  • South Africa
  • Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / genetics

Substances

  • Adaptor Proteins, Signal Transducing
  • DNA-Binding Proteins
  • ICOS protein, human
  • IL1R1 protein, human
  • IRF1 protein, human
  • Immunoglobulin J Recombination Signal Sequence-Binding Protein
  • Inducible T-Cell Co-Stimulator Protein
  • Interferon Regulatory Factor-1
  • RBPJ protein, human
  • Receptors, Interleukin-1 Type I
  • TRAF3IP2 protein, human
  • Tumor Necrosis Factor Receptor-Associated Peptides and Proteins
  • DNA-Directed DNA Polymerase
  • REV3L protein, human
  • PTPN22 protein, human
  • Protein Tyrosine Phosphatase, Non-Receptor Type 22